Ahaziah's downfall came from God when he went to visit Joram. When Ahaziah arrived, he went out with Joram to meet Jehu son of Nimshi, whom the LORD had anointed to destroy the house of Ahab.

2 Kings 9:3
Then take the flask of oil, pour it on his head, and declare, 'This is what the LORD says: I anoint you king over Israel.' Then open the door and run. Do not delay!"

2 Kings 9:6
So Jehu got up and went into the house, where the young prophet poured the oil on his head and declared, "This is what the LORD, the God of Israel, says: 'I anoint you king over the LORD's people Israel.

2 Kings 9:7
And you are to strike down the house of your master Ahab, so that I may avenge the blood of My servants the prophets and the blood of all the servants of the LORD shed by the hand of Jezebel.

2 Kings 9:21
"Harness!" Joram shouted, and they harnessed his chariot. Then Joram king of Israel and Ahaziah king of Judah set out, each in his own chariot, and met Jehu on the property of Naboth the Jezreelite.

2 Kings 9:27
When King Ahaziah of Judah saw this, he fled up the road toward Beth-haggan. And Jehu pursued him, shouting, "Shoot him too!" So they shot Ahaziah in his chariot on the Ascent of Gur, near Ibleam, and he fled to Megiddo and died there.

2 Chronicles 10:15
So the king did not listen to the people, and indeed this turn of events was from God, in order that the LORD might fulfill the word that He had spoken through Ahijah the Shilonite to Jeroboam son of Nebat.

2 Chronicles 22:6
so he returned to Jezreel to recover from the wounds they had inflicted on him at Ramah when he fought against Hazael king of Aram. Then Ahaziah son of Jehoram king of Judah went down to Jezreel to visit Joram son of Ahab, because Joram had been wounded.

And the destruction of Ahaziah was of God by coming to Joram: for when he was come, he went out with Jehoram against Jehu the son of Nimshi, whom the LORD had anointed to cut off the house of Ahab.